(1) Field of the Invention
The present invention relates to a root canal filling point which is used to fill a root canal after pulpectomy (extirpation of the pulp). More particularly, the present invention relates to a new root canal filling point which is physicochemically stable, is not toxic to periapical tissue, can be sterilized easily and X-rayed; and has high elasticity and fracture resistance which enable this root canal filling point to be pressure-inserted into an even narrow or curved root canal.
(2) Description of the Prior Art
Dental caries that develops in enamel spreads to dentine and eventually reaches to the pulp, causing pulpitis. Pulpitis is treated by extirpating the infected pulp and filling root canal (see FIGS. 1 and 2).
Teeth are comprised of enamel (1), dentine (2), cement (3), root canals including pulp (4), and apical holes (5). Apical holes (5) are connected to the surrounding periapical tissue. A typical procedures for filling a root canal following pulpectomy are as follows: After infected pulp is removed, root canal is expanded using a reamer (6) and filled with a root canal filling point (7). The gap between the root canal filling point (7) and the root canal wall is filled by a root canal filling sealer (8), and the apical hole is closed.
Root canal filling point should have the following characteristics: (A) it can be easily sterilized, (B) it is not deleterious to the surrounding periapical tissue, (C) it can be easily inserted into narrow and curved root canals by pressure-filling, (D) it can tightly seal the root canal wall and apical holes, (E) it does not shrink or deteriorate after root canal filling, (F) it can be X-rayed, and (G) it can be removed when necessary (Grossman L. I.: Endodontic practice, 10th edition, p 279 LEA and FEBIGER Philadelphia, 1981).
Gutta-percha point, which is made of macromolecular polymers (consisting of isoprene monomer) and zinc, is commonly used to fill root canals. However, root canal filling point made of gutta-percha has the following disadvantages: 1) it cannot be sterilized by any methods other than gas sterilization, 2) due to it's low elasticity and fracture resistance, it cannot be easily pressure-inserted into narrow and curved root canals, 3) it tends to be weakened under normal usage conditions, and 4) it is subjected to phagocytosis in the body.
Silver point have also been utilized. However, because it is extremely difficult to remove it once it is inserted, the silver point is seldom used today.
Points made of such materials as acrylic, epoxy resin, nylon, teflon, polyvinyl, polypropylene, polyethylene, and silicone have been produced experimentally. Of these, points made of polypropylene or polyethylene showed some potential for clinical application, but when a filler was added to these points so that they could be X-rayed, their physicochemical properties were adversely affected. As a result, such points were never developed for clinical use. Incidentally, the type and contents of the fillers used for these points have not been reported in documents (Grossman L. I.: Trans. Third International. Conf. Endodont., Univ. Pennsylvania Press, Phila., p 125, 1963).